Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 AM EST Sat Dec 07 2024

Valid 00Z Sun Dec 08 2024 - 00Z Sun Dec 15 2024

The combination of an initial surface trough left over from a
dissipated front, along with a front approaching from the
northwest by Sunday (but likely not reaching the main islands)
will tend to keep winds on the light to moderate side, with a
combination of some background trades but also sea breeze
influence.  This pattern will support varied focus for showers
through the weekend.  Guidance is consistent in developing
stronger trades next week as high pressure prevails to the north,
still with the greatest wind speeds likely in the
Wednesday-Thursday time frame.  The trades will support greater
windward/mountain shower focus.  

Today's dynamical guidance still shows shortwave energy aloft
pulling southward to the east of the state early next week and
then closing off an upper low that retrogrades south of the state
through mid-late week, but with a modest southward adjustment that
is enough to reduce precipitable water increases near the Big
Island versus what guidance was showing 24 hours ago.  However
latest ECens means still bring somewhat more moisture to the area
versus the GFS/GEFS mean and for a longer duration than in the 00Z
ECMWF.  00Z machine learning models show some interesting changes
from yesterday, as they generally delay the closed low formation
and retrogression compared to the dynamical guidance.  This
scenario ends up leading to some increase of rainfall over the
eastern islands toward late Friday or Saturday.  An average of
latest dynamical models/means provides a reasonable starting point
for a deterministic forecast but with an eye toward any possible
trending in future runs.

Rausch